I would like to find 4 photographers who would be interested in
sharing a Snow Coach some time during the last weeks of
January or early February 2015. This is not a tour, or workshop, but
just a group of like minded photographers who love Yellowstone in the Winter.
The snow coach driver would stay at any given spot as long as we want.
We would split the charter cost of the snowcoach. Lodging, Meals etc
are on your own. Please contact me if you are interested.

GNPA and CNPA members have an annual winter trip to Yellowstone. It's a small number of members as you describe - and open to non-members. I've been on this trip in earlier years and it is excellent. When I was part of the trip, I flew in a couple of days earlier, stayed in Gardiner and spent some time in Lamar Valley using my own rental car.

Here is their information:
Bob Waters of the CNPA and the GNPA’s Chris Dekle will again host a Winter, 2015 trip to Yellowstone National Park. You won’t want to miss it. Our past 3 trips have been loved by all who went.

DATES in Park: 5 Full Days in Yellowstone! January 31-February 4 (return to Bozeman on the 5th) and a second trip, Feb 6-10 (return to Bozeman on the 11th), 2015